Effects of flattening filter (FF) and flattening filter-free (FFF) beams on small-field and large-field dose distribution using the VMAT treatment plan

Abstract

Introduction: The aim of the study was to evaluate the influence of flattening filter (FF) and flattening filter-free (FFF) beams on small-field and large-field dose distribution using the VMAT treatment plan. Material and methods: Dose distribution calculations were performed for the VMAT technique in two locations: the larynx (small irradiation field; average 30.1 cm2) and gynecology (large irradiation field; average 173.1 cm2) using X-6MV flattening filter (FF) and flattening filter-free (FFF) beams. The following values were compared: the number of monitor units, minimum doses, average doses in PTV and maximum average doses in OaR (spinal cord – in larynx radiotherapy, bladder and rectum - in gynecological radiotherapy) and RPI (Radiation Planning Index) coefficient. Results and Discussion: The performed statistical tests indicate that there is a significant difference (p <0.05) between the number of monitor units in the irradiation of large (gynecological) fields between the FF and FFF beams. The dose distributions show no statistically significant differences between the flattening filter and flattening-free filter beams (regardless of the field size). Conclusions: Due to the smaller number of monitor units, it is recommended to use flattening filter beams (FF) for large-field radiotherapy.

Comparison of the dose distribution of the VMAT radiotherapy technique depending on the beam used: FFF-X10MV and FFF-X15MV

“…FF-X15MV, depending on the size of the treated volumes. Expanding on an earlier publication [ 11 ] allows for confirmation of previously drawn conclusions: for S-PTV, i.e., laryngeal tumors, no statistically significant differences were found between the kind of beams (FF or FFF) used and the parameters analyzed in the study. In the case of the analysis of L-PTV, i.e., gynecology neoplasms with lymph nodes, during the analysis, statistically significant differences were shown in the number of monitor units and doses in PTV.…”

“…In order to compare dose distribution for different types of beams in analyzed locations, RPI was used [ 12 ]. The obtained results were compared with data from the work of D. Plaza and K. Orzechowska [ 11 ].…”

“…Flattening filter-free (FFF) beams are most often used for stereotactic radiosurgery. It is a type of radiotherapy used in most cases for small cancers with few fractions that contain high doses [8][9][10][11]. Despite this use of radiation, normal tissues near the target area get only small doses of radiation.…”

“…In brief, RPI analyzes doses at targets and OARs to calculate values between 0 and 1. Extreme values are theoretical, where 0 means that OARs get a homogeneous maximal dose and 1 means that OARs get no dose [11,12]. Therefore, a comparison of dose distributions for two different VMAT beams applied to different locations of irradiated volumes associated with the PTV dimension can be useful in making clinical practice decisions related to treatment planning [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29].…”

Basic Characteristics of Dose Distributions of Photons Beam for Radiotherapeutic Applications Using YAG:Ce Crystal Detectors

“…The two dosimetric parameters describing a therapeutic beam of radiation generated by a conventional medical accelerator are uniformity and flatness. These factors characterize the intensity (dose) of radiation in the plane perpendicular to the beam axis (CAX) [ 1 , 2 , 3 , 4 , 5 , 6 ].…”